Platelet bound IgG levels in patients with systemic lupus erythematosus.

Platelet bound IgG (PBIgG) measured by antiglobulin consumption assay was compared with indices of clinical and laboratory disease activity in 37 nonthrombocytopenic patients with systemic lupus erythematosus. There was no correlation with clinical disease activity. When patients with a PBIgG level over 50 ng/10(7) platelets were compared to those with normal PBIgG levels (less than 20 ng/10(7) platelets), however, they had a significantly higher DNA binding level (p less than 0.05). In 17 patients there was no correlation between PBIgG levels and circulating immune complexes as measured by the Raji cell assay. Ten patients with PBIgG levels over 50 ng/10(7) platelets were followed for a mean of 23 months (5-26 months). None developed thrombocytopenia.